The present invention relates to apparatus for ensuring heat exchange between a gas flow and a heat exchanger.
As energy becomes more expensive it becomes more important to use energy efficiently. In many industrial processes it is necessary to transfer energy between a gas flow and a heat exchanger and it is desirable that this transfer should be as efficient as possible. Furthermore, if more efficient energy transfer can be achieved it becomes economic to recover energy exhausted from industrial processes. For example, the air exhausted from an industrial process or from an air conditioned building may be at a temperature either above or below the ambient temperature and this temperature difference represents energy which it is desirable to reclaim.
Air is supplied to paint spray booths, particularly where water-based paints are used, which is conditioned to a controlled temperature and humidity. This air is then exhausted to atmosphere. Large volumes of air must be conditioned with a consequent expenditure of energy and accordingly it is desirable to recover this energy from the exhaust air.
It has been proposed to pass the exhaust air from a spray booth over heat exchanger coils in which a heat transfer medium flows such that the heat transfer medium is heated or cooled by the exhaust air. For example, in one project the heat exchanger coils contain the condenser fluid from a refrigeration plant and this condenser fluid is cooled by the exhaust air from a paint spray booth.
Of course, the transfer of heat to or from the heat transfer medium in the heat exchanger coils should be as efficient as economically possible.
It is known that where exhaust air is passed over heat exchanger coils the heat transfer rate can be improved by wetting the coils with a liquid. Thus, where the heat transfer medium is to be cooled the liquid on the coils is evaporated and passes into the air flowing over the coils. The evaporation of liquid absorbs heat from the heat exchanger coils.
However, wetting of the coils only significantly increases the efficiency of the heat transfer if the coils are thoroughly wetted.
It is an object of the present invention to provide apparatus for ensuring heat exchange between a gas flow and a heat exchanger in which heat is transferred efficiently.